The present invention relates to a gaze-fixing device installed or incorporated in a surgical microscope and adapted to fix the gaze of a patient to be operated on, and, more particularly, to a gaze-fixing device useful for radial keratotomy.
In recent years, surgical operations of radial keratotomy (hereafter referred to as the "RK operation") have come to be undertaken in which radial cuts are provided in a cornea for treating abnormalities of refraction of an eye, such as myopia and astigmatism. It is necessary to provide a marking at the central position of the cornea so as to effect this RK operation.
For this purpose, a conventional surgical microscope has a gaze-fixing device whereby, as shown in FIG. 7, the patient being operated on is made to gaze at a light source LS of a concentric illuminator CI, along a visual axis VA a reflected image F' of the filament F of the light source LS formed by the cornea C of the eye E to be operated on is observed by a microscope MS, and a cornea-passing point P of a principal ray PR from this reflected image F' is marked as the center of the cornea.
With this conventional device, as can be seen from FIG. 7, since the eye to be operated on gazes at the filament F of the light source LS, the visual axis VA thereof differs from the observation optical axis OA for observing the reflected image F' of the microscope MS, and also differs from the principal ray PR directed from the reflected image F' to an observation optical system.
Consequently, if a conventional device is used, a marking cannot be provided at the real center Q of the cornea where the visual axis VA passes through the cornea C, so that there has been a drawback that the marking is provided at the cornea-passing point P of the principal ray PR, which is different from the same.
In addition, the conventional device has had another drawback in that stimulus on the fovea centralis macula retinae of the eye to be operated on is too strong since the patient fixes his gaze on the filament of a high-illuminace light source which is used during the operation. Furthermore, although the conventional surgical microscope is provided with a light quantity-adjusting means, the adjusting means is installed at the power source portion of the microscope. Hence, the operator, who has undergone sterilization treatment, cannot operate it directly, and an assistant has been necessary. This problem of adjusting the quantity of illumination light arises not only in connection with the RK operation alone, but also in connection with other ophthalmologic operations.